1. Field of the Invention
Embodiments of the present invention relate to electric lawn mowers that may be used outdoors for mowing grass or the like.
2. Description of the Related Art
Known lawn mowers generally include a mower body and a handle. The mower body is typically provided with wheels. The handle extends obliquely upward in a rearward direction from the mower body. The user may grasp the handle and push the mower body to move the same for performing a lawn mowing operation. The mower body may have a cutting blade that is rotatably driven by an electric motor as a drive source. In general, the motor is disposed within the mower body with its axis oriented in the vertical direction. The cutting blade rotates within a horizontal plane about the motor axis at a position along the lower surface of the mower body. Therefore, changing the vertical position of the wheels relative to the mower body can change the cutting height or the mowing height. EP0829196A2 (also published as Japanese Patent No. 3160759 and U.S. Pat. No. 5,910,091), U.S. Pat. No. 5,806,374 (also published as Japanese Patent No. 3329654), U.S. Pat. No. 5,736,837 (also published as Japanese Patent No. 3553277) and EP1285568A1 (also published as Japanese Patent No. 3776772 and U.S. Pat. No. 6,658,829) teach various techniques regarding electric lawn mowers.
In addition to electric lawn mowers driven by an AC power source, there have been proposed DC powered electric lawn mowers that can use batteries serving as DC power sources. When a DC powered electric lawn mower is used, the user does not need to lug a long power cord, and therefore, the performance (usability) in handling the lawn mower outdoors may be improved and the mowing operation can be efficiently performed. The battery may be removed from the tool body for recharging by a battery charger, so that the battery can be repeatedly used.
In recent years, battery packs having a battery case and a plurality of lithium-ion battery cells disposed within the battery case have been broadly used as batteries for power tools, etc. Therefore, there have been proposed electric lawn mowers having lithium-ion battery packs as power sources.
A device for preventing the unintentional use of an electric lawn mover has been proposed. For example, a key has been used in the operation of a start switch for starting the electric motor. The engine can only be started when the key has been inserted into a given key insertion portion and moved to an operable position. With this device, any person who does not have a key and is not authorized to use the lawn mower, cannot start the electric motor. However, it may be possible that the user forgets to remove the key from the key insertion portion.
There is the need in the art for an improvement in the usability of an unauthorized use preventing device for an electric mower.